Many freshwater applications suffer degraded performance due to buildup of scale, bacteria and corrosion. Current water treatment systems focus on use of often harsh chemicals to limit the effects of this buildup. In addition, use of chemicals is time consuming and expensive. Chemicals must be added frequently, water chemistry monitored through frequent sampling and analysis, and periodic flushing, shocking and similar operations still are required. Even with the most sophisticated chemical treatment system, some scale buildup will occur, particularly in high temperature components such as heat exchangers and steam generators. Table 1 shows the impact of scale buildup on performance of a heat exchanger.
TABLE 1Increase in Energy Consumption as a Function of Scale ThicknessScale ThicknessIncreased Energy(Inches)Consumption (%) 1/328.5 1/1612.4⅛25¼40
Many devices currently available use one or more solenoid coils to prevent scale and bacteria growth in water that passes through the coils. Some current devices use microprocessors to generate the waveform used to adjust pulse frequency. However, most current devices use standard analog techniques to provide signals to their coils, which do not have the flexibility to change the use of any coil between AC and DC signals or to allow different settings of signal amplitude adjustment for different waters or operating conditions.
One such device is the Dolphin, manufactured by Clearwater Systems, Inc. (U.S. Pat. No. 7,524,424) this device uses a microprocessor to pack more pulses into a given half cycle, but there is no user interface or other provisions for modification of signal output to account for varying water conditions. In addition although it has more than one coil, they are operated in series so behave electrically as a single unit and there is no provision for different signals to different coils.
Another such device is the Pulse˜Pure manufactured by Evapco (US Patent Application 2007/0114164). Whereas this device does have provisions for AC and DC coils, there is no flexibility to allow changing signals in the field if the conditions warrant. In addition, the resonant frequency must be determined at the factory and adjusted with trimmer capacitors. There is no provision for automatic tuning of the circuit or any adjustments an operator could make in the field to alter treatment characteristics to compensate for differences in water quality or character.